1. Electromagnetism

2. Magnetic field around a current carrying conductor-
Magnetic flux
Grip rule : If the conductor is gripped with right hand, with the thumb extended in the direction of current, the fingers wrapped around the conductor indicate the direction of field. +
ELE101/102
Dept of E&E,MIT Manipal

3. Magnetic field produced by a solenoid
Grip rule: If the coil (solenoid) is gripped with the right hand, with the fingers pointing in the direction of current, then the thumb out- stretched parallel to the axis of the coil points in the direction of the magnetic field inside the solenoid
Field
ELE101/102
Dept of E&E,MIT Manipal

4. Force acting on a Conductor
A current carrying conductor, placed in a magnetic field, produces a force.
This force can be increased,
When the current in the conductor is increased
When length of conductor is increased
When the magnetic field is made stronger
Force on the conductor =
f lux density  length of conductor  current
or f = B I l Newton
Note: considering single conductor
ELE101/102
Dept of E&E,MIT Manipal

5. Direction of Force: Fleming’s left hand rule
Mechanical force exerted on the conductor always acts in a direction perpendicular to the plane of the conductor and the magnetic field
Field
(Mechanical force)
Current
(Second finger)
thumb
(First finger)
This is the principle of electric motor
ELE101/102
Dept of E&E,MIT Manipal

6. Electromagnetic Induction
An EMF is induced in a conductor if the following conditions are satisfied:
Magnetic field
Conductor in the vicinity of magnetic field
Magnetic field linking with conductor changes OR Relative motion between the Conductor & Field
Faraday’s laws of
Electromagnetic Induction
When a conductor cuts or it is cut by
magnetic flux, an emf is induced in the conductor.
The magnitude of the induced emf is proportional
to the rate at which the conductor cuts or is cut by
the magnetic flux
ELE101/102
Dept of E&E,MIT Manipal

7. Electromagnetic Induction
Direction (Polarity) of induced emf:
Lenz’s law:
An electro magnetically induced emf always acts in such a direction to set up a current opposing the motion or change of flux responsible for inducing the emf.
ELE101/102
Dept of E&E,MIT Manipal

8. Fleming's right hand rule
Right hand rule: If the first finger of the right hand is pointed in the direction of the magnetic flux, and if the thumb is pointed in the direction of motion of the conductor relative to the magnetic field, then the second finger, held at right angles to both the thumb and the first finger represents the direction of emf.
Field
(First finger)
(thumb)
Motion
(second finger)
Emf
ELE101/102
Dept of E&E,MIT Manipal

9. Induced emf
Statically induced emf: - The voltage induced in the conductor due to change in the magnetic field
Conductor is stationary
Magnetic Field is changing in a stationary Magnetic System;
Ex: Transformer
Dynamically induced emf: - The voltage induced in the conductor due to relative motion of conductor and magnetic field
Conductor is moving/stationary
Magnetic Field is stationary/moving
ELE101/102
Dept of E&E,MIT Manipal